An organic electroluminescence device (hereinafter, occasionally abbreviated as an organic EL device) using an organic substance is a promising component of a solid-emitting-type full-color display device of a low cost and a large area. Accordingly, various developments of the organic EL device have been made.
The organic EL device generally includes a pair of opposing electrodes and an emitting layer interposed between the pair of opposing electrodes. When an electrical field is applied to the opposing electrodes of the organic EL device, electrons are injected from a cathode and holes are injected from an anode. When the injected electrons and holes are recombined in the emitting layer, excitons are formed. Energy generated when the excitons are returned from an excited state to a ground state is irradiated as light. The organic EL device emits light in accordance with such a principle.
A typical organic EL device exhibits a higher drive voltage than an inorganic light-emitting diode. Moreover, since properties of the organic EL device are considerably deteriorated, the organic EL device is not in practical use. Although the organic EL device has been gradually improved in recent years, further lower drive voltage and higher efficiency have been demanded.
Patent Literature 1 (JP-A-2006-176448) discloses an organic EL device including a compound having an anthracene skeleton in at least one of an electron injecting layer and an electron transporting layer. Patent Literature 2 (US Patent Application Publication No. 2006/0019116), Patent Literature 3 (US Patent Application Publication No. 2007/0205412), Patent Literature 4 (Korean Publication Patent No. 10-2009-052774), Patent Literature 5 (Korean Publication Patent No. 10-2010-066424), Patent Literature 6 (Korean Publication Patent No. 10-2009-086015), Patent Literature 7 (International Publication No. WO2010/005268), Patent Literature 8 (International Publication No. WO2010/114263), Patent Literature 9 (US Patent Application Publication No. 2011/0084259), Patent Literature 10 (JP-A-2011-173972), Patent Literature 11 (US Patent Application Publication No. 2011/0215308), Patent Literature 12 (JP-A-2011-243597), Patent Literature 13 (US Patent Application Publication No. 2011/0295017) and Patent Literature 14 (US Patent Application Publication No. 2011/0315963) each disclose an organic EL device including an electron injecting layer and an electron transporting layer.
Although having an improved lifetime as compared with that of a typical organic EL device, the organic EL devices of Patent Literatures 1 to 14 are required to exhibit a further lower drive voltage for practical use.